This invention relates generally to rototillers and cultivators for gardening, and more particularly to the transmission housing for such devices.
Rototiller devices are commercially available for home gardening applications. Such devices dig up and turn over top soil by the use of mechanically driven disks containing teeth on the disks' periphery. These rotating disks, known as tines, dig into the earth and turn over soil at that location in order to prepare the soil for planting. Although rototiller design may vary, usually the rototiller rests upon the tines. Because these tines are driven to rotate, in order to dig and tear up the soil, the rototiller tends to crawl in the direction of the spinning tines when the tines engage the ground.
Power for such prior art rototillers usually is provided by an engine, be it gasoline powered or electric powered. In either case, the engine operates through a transmission to rotate the tined axle.
The rototiller is guided in its action by the operator through the use of a pair of handle bars that may or may not support a clutch control means to engage the engine and tined shaft. As with any transmission, a lubricating system is required to minimize wear of the intermeshing gear parts. Lubricating material (e.g., grease or oil) must be retained and/or replaced periodically to maintain transmission operation. However, alignment holes and lubrication injection ports within the housing increase the likelihood of lubrication material leakage through these apertures. Moreover, the tined axle itself is a source of leakage since the axle must be free to rotate even though it is directly coupled to the transmission.
The following constitute examples of various types of prior art rototillers' or cultivators' transmissions suitable for home garden tilling/cultivating applications found in the following U.S. Pat. Nos.: 2,679,200 (Johnson); 2,755,718 (Arndt); 2,847,924 (Quick); 2,864,293 (Edrich et al.); 2,908,337 (Surprise); 3,202,004 (Field); 3,123,149 (White); 3,442,335 (Silbereis et al.); 3,452,823 (Shapland, Jr.); 4,250,968 (Fox) and 4,421,176 (Tuggle et al.).
The clutch mechanisms used with the rototiller transmissions vary. For example, some utilize belt/pulley tension clutches, while others use centrifugal clutches or spring loaded clutches to engage or disengage or even reverse tined axle motion. Such designs can increase the size of the transmission housing or adjacent housing in order to accommodate the clutch.
One particularly effective rototiller for home gardening applications is sold by the Mantis Manufacturing Company of Huntingdon Valley, Pennsylvania under the trademark MANTIS TILLER/CULTIVATOR. This rototiller utilizes a gasoline powered engine to drive a worm gear transmission to rotate plural tined blades mounted on a common axle. The worm gear transmission is housed in a unitized compartment such that the primary components (e.g., a drive shaft, worm shaft and worm gear) are mounted and permanently enclosed within this compartment at the factory. This unitized design requires that openings in the housing be provided so that the primary components can be assembled inside the housing. This is accomplished by inserting the drive shaft through the top opening of the housing, while the worm shaft is inserted through an aperture in the bottom. The worm gear is inserted through the main housing opening and then the tined axle is inserted through the tined axle aperture and screwed into the worm gear center threading.
While the transmission housing is generally suitable for its intended purposes, it nevertheless leaves something to be desired from the standpoints of ease of assembly, ease of adjustment or maintenance of the transmission components, and long term resistance to lubrication leakage or loss. For example, with regard to initial assembly, there is no direct access to the worm shaft, worm gear or drive shaft. Thus, alignment of these components can only be monitored through the various openings through which these components were placed into the housing. Moreover, adjustments or corrections can only be accomplished by releasing the tined axle to free up primary component movement.
With regard to maintenance, any primary component needing repair or replacement requires removal of the tined axle. This latter step cannot be accomplished without damaging the tined axle bearings and seals. If, in the process of releasing the tined axle, the housing is scored or damaged the usual result is that any new seals or bearings installed will not seal as tightly as before the maintenance work was conducted.
With regard to the transmission housing, the main housing cover acts as a potential source of lubrication leakage. Since the worm gear must be introduced through this opening, alignment checked through this opening and customer maintenance (including adding lubrication) is accomplished through this opening, all of these increase the chance that this opening may leak.
Another commercially available rototiller for home gardening applications is that sold under the trademark "LI'L HOE" by Hoffco, Inc., of Richmond Indiana. This rototiller includes a die cast transmission housing formed of two components or sections which are screwed together to form an interior chamber in which the transmission components are located. The axle for the rototiller's blades extends through bushing mounted in the housing sections. Plural strengthening fins extend outward radially from the openings in the housing sections in which the axle bearings are located. In order to prevent the leakage of the internal lubrication a bead of a sealant or caulk is provided on the engaging surfaces of the two housing sections. Each housing section also includes a horizontal recess therein for receipt of the lower portion of a respective one of the rototiller's handle bars. Each recess includes a stop surface to ensure that the handle bar is mounted in the desired direction on the housing.